Breech mechanism



April 21, 1970 MAILLARD 3,507,187

BREECH MECHANISM Filed April 1, 1968 4 Sheets-Sheet 1 April 21, 1970 B. MAILLARD BREECH MECHANISM 4 Sheets-Sheet 2 Filed April 1, 1968 rm r 9 M w w w w w m wwhshshww Nh @m QM o 06 m .o /4 m m m 7 an &, MN \m Q 1 N 1 WN I QN v T I Q mm u 1 5mm QM mm A ril 21, 1970 B. MAILLARD BREECH MECHANISM Filed April 1, 1968 4 Sheets-Sheet 5 'B. MAILLARD BREECH MECHANISM A ril 21, 1970 4 Sheets-Sheet 4 Filed April 1, 1

United States Patent 54,003 Int. Cl. F41d 1/08, 5/04 US. Cl.- 89-185 24 Claims ABSTRACT OF THE DISCLOSURE The breechblock slides in a casing which in turn slides non-rotatably in the breechcase. Mechanical means transform into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, when the breechblock has substantially reached its front closing position, for locking the breechblock by co-operation between the barrel and locking lugs formed on the breechblock. At least a portion of each one of (a) the external surface of the locking lugs, (b) the external surface of the casing and (c) the internal surface of the breechcase, lies on a common geometrical cylinder of revolution such that the breechblock is guided along the internal surface of the breechcase by the engagement both of the external surface of the lugs and the external surface of the casing on the internal surface of the breechcase.

The present invention relates to breech mechanisms for automatic and semi-automatic guns of the type including a breechblock adapted to be locked by rotation and which is provided, on the one hand, at the front part thereof, with a cup-shaped recess in which is engaged the rear part of a cartridge to be fired, and, on the other hand, on the outside, with locking lugs which co-operate with lugs provided in a sleeve rigid with the gun barrel, the breech mechanism further comprising a casing surrounding the breechblock and slidable longitudinally without rotation in a breechcase, means being provided between said casing and the breechblock to transform into a rotary movement of the breechblock (which is then locked) at least a portion of the translatory motion that takes place between the casing and said breechblock once the latter reaches substantially its front closing position.

The object of the present invention is to provide a breech mechanism which is better adapted to meet the requirements of practice than those known at the present time.

According to a first feature of the present invention, in a breech mechanism of the type indicated above, there are provided on a common geometrical cylinder of revolution, on the one hand, the external surface of the breechblock lugs and at least a portion of the external surface of the casing surrounding the breechblock, and on the other hand, at least a portion of the internal surface of the breechcase, whereby the breechblock is guided along this portion of the internal surface of the breechcase not only by the casing but also by at least some of the breechblock lugs. For the sake of convenience, said portion of the internal surface of the breechcase will be called hereafter cylindrical portion, it being understood that this portion does not necessarily form an entire cylinder, but may form only part or parts of a cylinder.

A second feature of the present invention consists, in a breech mechanism of the type indicated above, in providing, in the lateral outer surface of the casing, two diametrically opposed longitudinal bosses, the lateral longitudinal faces of which co-operate with guiding faces provided in the breechcase for the purpose of preventing 3,507,187 Patented Apr. 21, 1970 the casing from rotating inside the breechcase, one of these bosses having a front face adapted to co-operate with a sear for stopping the breech mechanism whereas the other of these bosses has a front face adapted to cooperate with the device for unlocking the breech mechanism from the breechcase, on the one hand, and with the resetting device, on the other hand, which last mentioned boss may possibly co-operate through the rear portion thereof with an ejector for rocking this ejector.

A third feature of the present invention consists, in a breech mechanismvof the type indicated above, in separating the lugs of the breechblock from one another by angular spaces one of which accommodates an extractor carried by the breechblock Whereas the angular space diametrically opposed to the preceding one extends as far as the inside of the cup-shaped recess to provide a pasage for an ejector carried by the breechcase.

A fourth feature of the present invention consists, in a breech mechanism of the type indicated above, in providing, on the one hand, directly between the breechblock and the casing, a blocking device adapted to work at the end of the unlocking of the breech mechanism, for irnperatively maintaining said casing in the extreme rear position with respect to the breechblock during the reciprocating movement of the breech mechanism inside the breechcase and, on the other hand, on the breechcase, a release device adapted to act, at the end of the breech mechanism closing operation, upon the blocking device for making it inoperative.

A fifth feature of the present invention consists, in a breech mechanism of the type indicated above, in distributing the breechblock lugs along at least two annular rows the rear active faces of which are located on two identical but distinct skew helical lines spaced axially at a distance from each other greater than the pitch of said helical lines.

The present invention further relates to breech mechanisms for automatic or semi-automatic guns of the type which comprise, on the one hand, a breechblock provided, at the front end thereof, with a cup-shaped recess into which is engaged the rear part of a cartridge to be fired, said breechblock being adapted to be locked with respect to an element rigid with the gun barrel, and, on the other hand, a locking member for controlling (control stroke) and maintaining (safety stroke) the locking of the breechblock, this member being mechanically connected with a firing pin movable with respect to the breechblock and subjected to the action of at least one firing spring bearing upon the breechblock. This invention is more especially, but not exclusively, concerned with breech mechanisms of the type first indicated above, wherein this locking member is essentially constituted by said casing and is adapted to rotate the breechblock in one direction (control stroke) so that the lugs it carries are screwed in front of the lugs carried by the breechcase, then to perform a safety stroke preventing the breechblock from rotating in the opposed direction.

A sixth feature of the present invention consists in a breech mechanism of this second type (and possibly also of the first type indicated above), in using a semi-positive connection between the firing pin and the locking member (casing) such that, when the locking member has only partly completed the safety stroke, the firing pin can reach the primer of the cartridge received in the cupshaped recess to fire it before the end of the safety stroke.

Preferred embodiments of the present invention will be hereinafter described with reference to the appended drawings given merely by way of example, and in which:

FIGURE 1 is a longitudinal sectional view of a breech mechanism made according to the present invention and of the gun elements that co-operate with this breech mechanism;

FIGURE 2 is a view similar to FIGURE 1 showing a breech mechanism made according to a first modification;

FIGURE 3 is a transverse sectional view, in particular on the line III--III of FIGURE 2, of one of the breech mechanisms of FIGURES l and 2;

FIGURE 4 is a separate view of the breechblock in longitudinal section analogous to that of FIGURES 1 and 2;

FIGURE 5 shows, from the left hand side of FIGURE 4, the same breechblock with, in cross section, the ejector;

FIGURE 6 is a view of the breechblock f FIGURE 4 seen form above;

FIGURE 7 is a longitudinal half-section showing some of the elements of FIGURE 1 in a different working position; and

FIGURE 8 shows, similarly to FIGURE 3, a breech mechanism made according to a second modification.

The particular embodiments illustrated by way of example in the drawings relate to automatic guns of calibre comprised between 20 and 40 mm.

The breech mechanism comprises a breechblock 1 which is locked by rotation, this breechlock including, on the one hand, at the front thereof, a cup-shaped recess 2 which engages the rear part of the cartridges to be fired (not shown) and, on the other hand, at the periphery thereof, locking lugs 3 adapted to co-operate with corresponding lugs 4 provided in a sleeve rigid with gun barrel 6. The breech mechanism further includes a casing 7 surrounding breechblock 1 and slidable longitudinally without rotation in 'breechcase 8. Means are provided between the casing 7 and the breechblock 1 for transforming into a rotary movement of the breechblock 1 (and to lock said breechblock by the intermediary of lugs 3 and 4) at least part of the translatory motion which takes place between the casing 7 and said breechblock 1 when said breechblock arrives substantially in its front closing position (position shown in FIGURES 1 and 2).

Breechblock 1 is made of a single piece (see, in particular, FIGURES 4 to 6) of substantially cylindrical shape about axis X-X which coincides both with the axis of rotation of this breechblock and with the axis of barrel 6. Said breechblock 1 projects from casing 7, at the rear thereof, through a hole 9, whereby the rear face 10 (FIGURE 1) or 10a (FIGURE 2) of said breechblock 1 co-operates with the conventional breech mechanism damping device 11 carried by the rear portion of breechcase 8.

In the embodiment of FIGURE 2, the rear face 10a of breechblock 1 co-operates directly with said damping device 11 (similar to that diagrammatically shown by FIG- URE 1). According to the embodiment of FIGURE 1, the rear face 10 of the breechblock 1 constitutes a bearing face for a plug 12 mounted on said breechblock by means of a bayonet joint 13, the rear of this plug being interposed between said face 10 and damping device 11.

Whatever be the embodiment that is chosen, breechblock 1 extends from the rear to the front of the breech mechanism and determines substantially (that is to say except for the thickness of plug 12) the length of the breech mechanism, which is thus greatly reduced.

To facilitate assembly, casing 7 is advantageously made of two casing elements or shells 7a and 7b adjoining each other along a diametral plane (plane of FIGURES 1, 2 and 7) and ridgidly interconnected in the longitudinal direction by radial studs 14 (forinstance one stud carried by easing element 7a located between two studs carried by easing element 7b, as shown by FIGURES 1, 2, 3 and 7).

A transverse spindle 15 extends acros breechblock 1 in a manner that will be hereinafter explained. This spindle is connected, inside breechblock 1, with a firing pin 16 (FIGURES 1 and 7) or 16a (FIGURE 2) to operate it; and spindle 15 is connected, outside this breechblock 1,

4 without play, to casing 7. Breechblock 1 is provided with a longitudinal recess 17 which, in the absence of a plug such as 12, is open towards the rear and receives the body of firing pin 16 and guides it with a translatory movement parallel to axis X-X. Furthermore, to accommodate firing pin 16 or 16a, breechlock 1 is. provided, at the front thereof, with a passage 17a which opens into cup-shaped recess 2.

According to the embodiments of FIGURES 1, 2, 3 and 7, spindle 15 has one end thereof engaged in the element 7a of casing 7 and the other end thereof in element 7 b. According to the modification of FIGURE 8, wherein the elements are designated by the same reference numbers as in the other figures, but increasd by 100, spindle 115, connected to firing pin 116, is located in the plane of assembly of elements 107a and 1071) and is therefore engaged, at each end thereof, half in element 107a and half in element 107b.

According to a first feature of the invention, the outer surface of the lugs 3 of breechblock 1 is located in the same geometrical cylinder of revolution C (FIGURES l, 2 and 5) as at least a portion of the outer surface of casing 7. The diameter D of this cylinder is equal to the inner diameter of a cylindrical portion 18 of breechcase 8, along which cylindrical portion 18 move lugs 3 and casing 7. It is pointed out that lugs 3, as visible in FIG- URES 1 and 2, are not located in the plane of these figures (see FIGURE 5), which explains why their lower outline does not coincide with the intersection of cylinder C and said plane.

Thus, during its reciprocating movement, breechblock 1 is guided along cylindrical portion 18 not only by contact with casing 7 (in the manner which will be hereinafter described) which is itself in contact with said portion 18, but also by direct contact of at least some of its lugs 3 with this portion 18.

In order to transform the translatory movement of breechblock 1 with respect to casing 7 into a rotary movement of said breechblock about the axis of the gun barrel when the breechblock reaches substantially its front closingposition, illustrated by FIGURES l and 2, spindle 15 carries two cylindrical rollers 19 (FIGURE 3) adapted to co-operate with partly helical surfaces 20 (see also FIGURE 4) provided in a cylindrical enlarged portion 21 of breechblock 1, at least one of the end faces 21a and 21b of this cylindrical enlarged portion 21 limiting the longitudinal movements between casing 7 and breechblock 1. As shown by FIGURE 4, each of said surfaces 20 comprises a helical rear portion of a length equal to a, which corresponds to the locking stroke of casing 7, and a rectilinear front portion parallel to axis X-X, of a length equal to b, which corresponds to the safety stroke of easing 7.

Cylindrical enlarged portion 21 has an external diameter equal to the inner diameter of the recess 22 provided in casing 7 to accommodate said portion 21. On either side of cylindrical enlarged portion 21, breechblock 1 includes two cylindrical surfaces 23 and 24 on which elements 7a and 7b fit in a relatively fiuidtight manner so as to form between them said recess 22 the length of which is sutficient to permit displacement of casing 7 with respect to cylindrical portion 21, elements 7a and 7b fitting together in a relatively fluidtight manner along their diametral plane of separation (plane of FIGURES 1 and 2).

For this purpose, elements 7a and 7b are provided with two inward annular projections 25 and 26 which limit recess 22 between them and the inner diameters of which are equal (with the approximation corresponding to clearance) respectively to the diameters of cylindrical surfaces 23 and 24 against which these projections are applied. Rear projection 26 has a front face 26a (forming the rear wall of recess 22) which, as shown by FIGURES 1 and 2, constitutes an abutment for the rear end face 21b of enlarged portion 21. Front projection 25 has a rear face 25a (forming the front wall of recess 22) which, as shown by FIGURE 7, constitutes an abutment for the front end face 21a of enlarged portion 21. The movement of easing 7 toward the front may further be limited by contact of the front face 25b of the projection 25 of said casing 7 with a shoulder 27 provided on breechblock 1 (FIGURES 1 and 2). Likewise, the movement casing 7 toward the rear may further be limited by contact of the rear face 26b of projection 26 either with the front face of plug 12 (FIGURE 7) or with projections 39 (FIGURE 2) pro vided at the rear end of breechblock 1. It should be noted that radial studs 14 are provided at the level of rear projection 26.

Thus, recess 22 is made practically fluidtight, the openings defined by surfaces 20 being closed by casing 7 whatever he the relative axial position thereof with respect to breech-block 1. Owing to this fiuidtightness, there is obtained a protection of the locking and unlocking mechanisms of the breechblock against the penetration of dust, sand, powder combustion residues and the like.

According to the modification of FIGURE 8, the means for giving breechblock 1 its rotary locking movement consist of two aligned radial trunnions 28 carried by breechblock 101. Said trunnions 28 carry respective cylindrical rollers 119 engages in partly helical surfaces 120 provided in casing 107. As shown by this FIGURE 8, trunnions 28 extend along a line at right angles to spindle 115. Reference character A indicates the amplitude of the angular displacement of breechblock 101 which produces its locking or its unlocking. Like surfaces 20 (FIGURE 4), surfaces 120 include, in addition to a helical portion, a rectilinear safety portion.

According to a second feature, the lateral outer surface of casing 7 forms two diametrically opposed longitudinal projections 29 and 30, the longitudinal faces 29a and 30a of which cooperate with guide faces 31 (FIGURE 3) provided in breechcase 8, so as to prevent casing 7 from turning inside said breechcase. Projection 29 is provided with a front face 29b adapted to cooperate with a sear 32 (FIGURE 1) to stop the breech mechanism in the open position whereas projection 30 is provided with a front face 3% adapted to cooperate with a device 33 (such as a push-piece actuated by a gastap in the gun barrel) provided for releasing the breechblock with respect to breechcase 8 (FIGURE 1), on the one hand, and with resetting device 34 (FIGURE 2) which permits of resetting breechblock 1 before the beginning of the firing, on the other hand. Projection 30 may still, according for instance to the embodiment of FIGURE 2, cooperate at the rear with an ejector 35 (FIGURE for rocking it. On the contrary, according to the embodiment of FIG- URE 1, it is the lower portion 38a of plug 12 that is arranged to rock ejector 35. Anyway, projection 30 is provided with a longitudinal groove 300 for the passage of a part of the ejector.

Preferably advantage is taken of the increased thickness corresponding to projections 29 and 30 to provide therein the radial studs 14, which, as stated above, extend inwardly as far as projection 26.

Concerning plug 12 (FIGURE 1), it advantageously comprises guiding means which cooperate with breechcase 8 both to hold the plug radially and to prevent it from rotating, this plug forming a support on the one hand, toward the rear, for a counter-recoil spring 36, and on the other hand, toward the front, for a firing pin spring 37 housed in the recess 17 of breechblock 1 at the rear of firing pin 16, Counter-recoil spring 36 bears, at the front, either against the plug 12 (FIGURE 1), or against casing 7 (FIGURE 2). The guiding means in question may consist of projections 38 which are integral with plug 12 and which have a profile analogous to that of easing 7 with its projections 29 and 30, which enables it to cooperate on the one hand with cylindrical portion 18 (FIGURE 3) for radial guiding and on the other hand with guiding faces 31 for maintaining a fixed angular position. The lower portion 38a of plug 12, which actuates the ejector, is then carried by the lower projection 38. Of course, bayonet joint 13 must be adapted to enable breechblock 1 to rotate with respect to plug 12 when said 'breechblock is locked or unlocked by rotation.

The breechblock is thus guided not only, as explained above, by at least some of its lugs 3 and casing 7, but also by plug 12. Due to the fact that said plug has a fixed angular position, counter-recoil spring 36 does not interfere with its operation.

In the embodiment of FIGURE 2, plug 12 is replaced by a plug 12a which is nearly wholly housed in the recess 17 of breechblock 1, without the possibility of being acted upon by counter-recoil spring 36, which can then bear against breechblock 1, or preferably, as shown, against the rear of easing 7. Plug 12a, which acts as rear support for firing pin spring 37, is provided with a longitudinal slot 40 so that it is possible to deform it resiliently by urging toward each other the projections 41 provided at the rear thereof, for introduction into recess 17. Then said projections 41 are allowed to move away from each other so as to engage into notches provided on the inside of breechblock 1 (as shown by FIGURE 2).

According to a third feature, the lugs 3 of the breech block 1 are separated from one another by angular spaces 0, d one of which accommodates an extractor 42 (FIG.- URES l and 2) carried by breechblock 1 whereas the angular space diametrically opposed to the preceding one extends as far as the inside of the cup-shaped recess 2 to provide a passage 43 (FIGURES 1, 2 and 4) for ejector 35 which is carried by the breechcase 8. In the embodiment shown by the drawings, an angular space of 360/ (Zn-H) is provided between the lugs 3 of the breechblock 1, where 211 is the number of lugs 3 (n being an integer). All the lugs 3 have the same peripheral development, so that, between two particular adjacent lugs 3 there is left an angular space c (FIGURE 5) greater than the angular space a extending between the other adjacent lugs taken two by two. This large angular space 0 accommodates extractor 42, whereas the small angular space a that is located opposite to said large angular space 0 forms part of passage 43.

Extractor 42 is housed in a slot 44 (FIGURE 4) provided between two lugs 3 and it is kept toward the front and radially toward the outside by a heel 42a carried by said extractor and engaged in a recess 45 of breechblock 1 so as to form a bearing and pivoting abutment as shown in FIGURES 1 and 2. This extractor is kept in position longitudinally toward the rear by a leaf-spring 46 which tends to make it penetrate into cup-shaped recess 2. Leafspring 46 is fitted at the rear into the cylindrical enlarged portion 21 of breechblock 1, said spring 46 being itself held longitudinally by an expansible ring 47. Breechblock 1 is provided with a passage 48 (FIGURES 4 and 6) whose width is equal to that of spring 46. Passage 48 extends rearwardly from recess 45 to the inside of enlarged portion .21, overhanging edges 49 being provided in said enlarged portion to hold spring 46 therein. Passage 48 is provided at the rear thereof with a cylindrical housing 50 whose axis is radial, and which is adapted to accommodate expansible ring 47. The latter is of a height such that it is kept in position by easing 7 as shown by FIGURES 1, 2. and 3.

According to the embodiment illustrated (see in particular FIGURE 5), n is equal to 3 so that breechblock 1 is provided with six lugs 3 spaced apart by 360/ 7, with the exception of the two upper lugs which are at 720/ 7 from each other. These angular spacings are measured from the middle axis of one lug to the middle axis of the next lug, and thus do not take into account the circumferential width of the lugs.

According to a modification (not illustrated), an angular space of l=/ (n+1) is provided between the lugs of the breechblock distributed in two symmetrical groups, where 2n is again the number of lugs which have substantially the same peripheral development. There are two diametrically opposed large angular spaces of 360 (n+1) one of which accommodates extractor 42 whereas the other provides passage 43.

According to a fourth feature there is provided, on the one hand, directly between breechlock 1 and casing 7, a blocking device adapted to come into play at the end of the unlocking of the breech mechanism, to hold casing 7 imperatively in its extreme rear position with respect to breechlock 1 (position illustrated by FIGURE 7), during the reciprocating movement of the breech mechanism in breechcase 8 and, on the other hand, on said breechcase, a release device located to act, at the end of the breech mechanism closing movement, upon the blocking device to put it out of action.

Preferably, said b'ocking device comprises a strip 51 (FIGURES l and 7) carried by breechblock 1 and the rear end of this strip is resiliently urged (preferably by the elasticity of the strip itself) radially away from the external surface of breechblock, that is to say into the path of the front face 26a of projection 26. The release device includes a piece provided with an inclined face 52 carried by breechcase 8, a push-piece 53 housed in casing 7 being interposed between said inclined face 52 and strip 51. Advantageously (as shown), said strip 51 has its front end tightly held in the rear part of enlarged portion 21, which is provided for this purpose with a passage 52 (FIGURE 4) limited at the front by projections 54a serving to wedge strip 51.

It should be noted that, in order to simplify the drawings, it has been supposed in FIGURES l, 2 and 3 that extractor 42, passage 43, spring 46 and strip 51 are located in the plane of assembly of shells 7a and 7b. In reality, this condition is complied with only when (contrary to the case of FIGURES l, 2 and 3) casing 7 is located in its extreme rear position with respect to breechblock 1, as shown by FIGURE 7 where strip 51 is shown correctly in said plane of assembly, due to the rotation of breechblock 1 with respect to casing 7 as permitted by the recoil movement of the latter.

According to a fifth feature, the lugs 3 of the breechblock 1 are distributed in two annular rows the active rear faces f of which are located along two skew helical surfaces H and H (FIGURE 6) identical to each other but distinct, and which are spaced apart in the axial direction by a distance I from each other greater then the common pitch p of said helical surfaces. Reference characters 3a and 3b designate respectively the two rows of lugs 3. The advantage of this construction consists in the lengthening of at least some of said lugs 3 in the axial direction. This is due to the fact that, if the faces f of all the lugs 3 were located in the same helical surface, as usual, their axial length could be at most equal to the differences between the pitch p and the axial length of the lugs 4 of sleeve 5 which must pass between the lugs 3a and 3b of the two successive rows.

Furthermore, each beginning 56 and each end 57 of the rows of lugs 3a and 3b advantageously line the large angular space (FIGURE provided for extractor 42 (FIGURES l and 2), which facilitates the machining of lugs 3 which would tend to be rather delicate in view of the offsetting of helical surfaces H and H According to a first solution, the helical surfaces H and H and also the helical surface H in which are located the front faces g of the rear lugs 311, have inclinations such that reversibility of the movement is prevented. The term inclination designates the angle between two planes passing through any perpendicular to the axis XX. of the helical surfaces, namely a plane tangent to this helical surface and a plane perpendicular to said axis. Reversibility means that a thrust exerted from left to right on breechblock 1, from the position shown by FIGURES l and 2, is capable of rotating said breechblock despite friction phenomenons.

In order to prevent reversibility the angle in question may be given a value of about 5 or less.

According to a second solution, helical surfaces H H and H have inclinations such that reversibility of the movement is permitted, the angle defined above being then generally at least equal to 6 or 7".

The lugs 3 of the breechblock 1 may also be distributed in at least one row Whose rear face f would be located in a plane perpendicular to the axis of the breechblock.

According to the preceding description, the gun comprises locking means (casing 7) for controlling (control stroke (1, FIGURE 4) and maintaining (safety stroke b) the locking of breechblock 1 with respect to an element (sleeve 5) rigid with the gun barrel 6, this means being mechanically connected with firing pin 16a movable with respect to breechblock 1 and subjected to the action of at least one firing pin spring 37 bearing upon the breechblock.

According to a sixth feature, which is preferably applied to the locking means described above but which may be applied to locking means of a different type (for instance adapted to operate locking members carried by a non-rotary breechblock), a semi-positive connection is used between the firing pin 16a and the locking means, such that, while the locking means (casing 7) have moved only a portion of the safety stroke, firing pin 16m can reach the primer of the cartridge (that is to say project into cup-shaped recess 2) and fire it before the end of said safety stroke.

According to the embodiment of FIGURE 2 it suffices for this purpose to provide firing pin 16a with a slot 55 elongated in the direction of the axis X-X, extending through firing pin 16a. Preferably, firing pin 16a is given a weight such that it opposes rebounding of the locking means or casing 7. This feature will be better understood by comparing the structure of FIG URE 2 with that of FIGURE 1 where spindle 15 extends through firing pin 16 through a hole leaving no longitudinal play and where the firing pin is of smaller volume and therefore less heavy.

Owing to the anticipated firing thus achieved, a higher rate of firing and an improved safety of operation are obtained.

The breech mechanism described above works as follows:

Before firing, casing 7 is held in a rear position by sear 32 (FIGURE 1) which co-operates with its face 291). Breechblock 1 is also held in a rear position. Casing 7 is further held in its rear position with respect to breechblock 1 (as shown by FIGURE 7) by the fact that strip 51, fixed to said breechblock, bears upon the face 26a of the casing. Firing pin 16 or 16a is also kept in its rear position, against the action of spring 37, with respect to breechblock 1 by spindle 15 rigid with casing 7.

By acting upon sear 32, the gunner releases the whole of the breech mechanism with casing 7. The whole breech mechanism is thrust in the frontward direction by counterrecoil spirng 36 and receives in cup-shaped recess 2 a cartridge which is introduced into barrel 6. Once pushpiece 53 comes to the level of inclined face 52, strip 51 is retracted into the position of FIGURES l and 2 and releases casing 7 with respect to breechblock 1. When said breechblock has reached approximately its closing position, shown by FIGURES l and 2, its lugs 3 come ahead of the lugs 4 of sleeve 5, which permits rotation of the breechblock. Firing pin spring 37, acting through firing pin 16 or 16a and spindle 15, drives toward the front casing 7 which is guided in such manner that it can have no movement of rotation about itself. It follows that spindle 15, which carries rollers 19, first assumes a movement corresponding to the helical portion a of inclined surface 20 (FIGURE 4), thus rotating breechblock 1 and screwing the lugs 3 thereof in asor, 187

front of the lugs 4 of sleeve 5. Then spindle 15, moving along the rectilinear portion b (safety stroke) of sur face 20, prevents a reversing of the rotation which would release the breechblock. At the same time, firing pin 16 or 16a is driven frontwardly and enters recess 2, thus firing the primer of the cartridge present in the barrel.

According to the embodiment of FIGURE 2 the longitudinal play permitted by slot 55 enables firing pin 16a to strike the primer before the end of the safety stroke b (advanced firing), then to come into contact with breechblock 1 which limits the forward movement of said firing pin. As the time of firing of the cartridge is of the order of of a second, casing 7 and spindle 15 keep moving forward up to the position (end of stroke) shown by FIGURE 2 and, in case said casing and spindle 15 rebound (for instance when the time of firing exceeds 2 of a second), they meet during their rearward movement, resulting from rebounding, the rear end of the slot 55 of firing pin 16a which, due to its weight, will stop their movement.

After the cartridge has been fired, the gases developed in barrel 6 (or any other equivalent device) cause pushpiece 33 to move rearwardly, breechblock 1 remaining stopped by its lugs 3. Spindle 15, which carries rollers 19, after having moved through safety stroke b, reaches helical path a and causes breechblock 1 to rotate in the unlocking direction. At the end of the unlocking stroke, the elements come back into their relative mutual positions of FIGURE 7 where they are maintained by strip 51. According as the gunner continues or not to act on sear 32, the breech mechanism is either driven again in the frontward direction or retained by said sear.

In view of the inclination of the faces 1 and g of the lugs 3 of breechblock 1 and of the corresponding faces of the lugs 4 of sleeve 5 (with or without reversibility), a longitudinal relative movement takes place during the locking and unlocking strokes.

This leads to the following advantages.

On the one hand, during locking, breechblock 1 can be in rotation (due to the relative longitudinal displacement of the casing caused by the firing pin spring and the counter-recoil spring 36) before it comes into abutment at the end of the frontward stroke (about 1.5 mm.), and on the other hand, during underlocking, breechblock 1, which drives the extractor in its relative rearward movement, permits of detaching the cartridge case to be extracted from the cartridge chamber when the residual pressure in the gun barrel is still relatively high and before the casing reaches the end of its unlocking stroke toward the rear.

In the case of reversibility, there is further obtained a self unlocking of the breech mechanism, after the controlled recoil of easing 7 in the safety stroke b (FIG- URE 4) owing to the thrust transmitted by the case of cartridge that has just been fired, which could, for example, permit the rate of fire to be increased.

While the above description discloses preferred embodiments of the invention, it should be understood that said invention is not limited thereto, as there might be changes made in the arrangement, disposition and form of the parts without departing from the spirit or scope of the invention.

I claim:

1. In a breech mechanism of the type for use with an automatic or semi-automatic gun comprising a breechblock mounted in a breechcase having a barrel cooperating therewith, said breechblock adapted to be locked by cooperation between the barrel and locking lugs formed on the breechblock, means at the forward end of the breechblock for receiving the rear end of cartridges to be fired, a casing non-rotatably mounted in the breechcase about and in radial supporting contact with the breechblock for longitudinal sliding movement in the breechcase, and mechanical means for locking the breechblock by transforming into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, which relative movement takes place when the breechblock has substantially reached its front closing position at which it closes off the rear end of the barrel, the improvement wherein: at least a portion of each one of (a) the circumferentially extending external surface of the locking lugs, (b) the external surface of the casing and (c) the internal surface of the breechcase, lies on a common geometrical cylinder of revolution, such that the breechblock is mounted in the breech case to be guided along that said internal portion of the breechcase which lies on said geometrical cylinder of revolution by the engagement of the said circumferentially extending external surface portion of at least some of the lugs on the said internal surface portion of the breechcase and also by the engagement of the external surface portion of the casing on the said internal surface portion of the breechcase.

2. A breech mechanism according to claim 1, wherein the casing is made up of two complementary, generally cylindrical shells adjoining each other in a diametral plane of said casing and rigidly connected together by studs extending radially through the casing.

3. A breech mechanism according to claim 2, wherein a firing pin is located within the breechblock and wherein the two shells are further connected to each other by a spindle which passes through the breechblock and which is connected at the interior of the breechblock to the said firing pin to actuate this firing pin.

4. A breech mechanism according to claim 3, wherein said mechanical means includes said spindle, and two cylindrical rollers on said spindle adapted to cooperate respectively with at least partly helical inclined surfaces provided in a cylindrical enlarged portion of the said breechblock, at least a portion of said enlarged portion being positioned to limit the longitudinal movement of the casing with respect to the breechblock.

5. A breech mechanism according to claim 4, wherein both forward and rearward of said enlarged portion the breechblock comprises cylindrical surfaces and said casing includes an internal cylindrical recess, the ends of which fit in a fluid-tight manner against the cylindrical surfaces of the breechblock, said recess being large enough in the radial direction to accommodate said enlarged portion and of sufficient length between said ends to permit longitudinal movement of the casing relative to the breechblock with respect to said cylindrical enlarged portion, the two shells fitting together in a relatively fluidtight manner along their diametral adjoining plane.

6. A breech mechanism according to claim 1, wherein said mechanical means includes a pair of radial projections in the form of coaxial spindles fixedly connected to the breechblock, respectively, two cylindrical rollers adapted to cooperate with at least partly helical inclined surfaces formed in the casing.

7. A breech mechanism according to claim 1, wherein the breechblock carries at its rearward end a plug having guiding means which cooperate with the breechcase for maintaining the plug radially and for preventing it from rotating, the rearward side of the plug serving as a support for a counter-recoil spring and the forward side of the plug serving as a support for a firing pin spring housed within the breechblock.

8. In a breech mechanism of the type for use with an automatic or semi-automatic gun comprising a breechblock mounted in a breechcase having a barrel cooperat-' ing therewith, said breechblock adapted to be locked y cooperation between the barrel and locking lugs formed on the breechblock, means at the forward end of the breechblock for receiving the rear end of cartridges to be fired, a casing non-rotatably mounted in the breechcase for longitudinal sliding movement, said casing surrounding the breechblock to guide and support the same while permitting longitudinal movement of the breechblock relative to the casing for causing said locking of the breechblock in the casing, mechanical means for locking the breechblock by transforming into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, which relative movement takes place when the breechblock has substantially reached its front closing position at which it closes off the rear end of the barrel, and an unlocking means for unlocking the breechblock after firing said casing including at least one portion which is substantially a cylinder of revolution, said portion having fixedly connected thereto and extending outwardly therefrom at least one longitudinal projection, said projection having lateral faces shaped to cooperate with guide faces formed in the breechcase to guide the casing during said sliding movement and also to prevent the casing from rotating relative to the breechcase, the said projection being positioned to cooperate with a scar means carried by the breechcase to selectively prevent forward movement of the casing and the breechblock.

9. A breech mechanism as claimed in claim 8 wherein said casing has fixedly connected to the exterior surface thereof a second longitudinal projection diametrically opposed to the first projection, said second projection also having lateral faces shaped to cooperate with guide faces formed in the breechcase to permit sliding movement and to prevent the casing rotating relative to the breechcase, said unlocking means comprising a push piece mounted in the breechcase for movement against the said second projection to unlock the breechblock.

10. A breech mechanism as claimed in claim 8 wherein said casing has fixedly connected to the exterior surface thereof a second longitudinal projection diametrically opposed to the first projection, said second projection also having lateral faces shaped to cooperate with guide faces formed in the breechcase to permit sliding movement and to prevent the casing rotating relative to the breechcase, including a manually operable means positioned in the breechcase to engage the said second projection to urge the casing rearwardly until the first projection of the casing cooperates with the said sear.

11. A breech mechanism as claimed in claim 8 wherein said casing has fixedly connected to the exterior surface thereof a second longitudinal projection diametrically opposed to the first projection, said second projection also having lateral faces shaped to cooperate with guide faces formed in the breechcase to permit sliding movement and to prevent the casing rotating relative to the breechcase, and including a means for holding the spent cartridges in the breechblock as the breechblock moves rearwardly, and said second projection being adapted to cooperate with an ejection means for ejecting spent cartridges from the breechblock.

12. A breech mechanism as claimed in claim 8 wherein the said casing is made up of two complementary, generally cylindrical shells adjoining each other in a diametral plane of said casing and rigidly connected together by studs extending radially through the casing, said radial studs being located in said longitudinal projection.

13. A breech mechanism as claimed in claim 12 wherein said casing has fixedly connected to the exterior surface a second longitudinal projection diametrically opposed to said first longitudinal projection, and radial studs connecting said shells of said casing also being located in said second longitudinal projection.

14. In a breech mechanism of the type for use with an automatic or semi-automatic gun comprising a breechblock mounted in a breechcase having a barrel cooperating therewith, said breechblock adapted to be locked by cooperation between the barrel and locking lugs formed on the breechblock, means at the forward end of the breechblock for receiving the rear end of cartridges to be fired, a casing non-rotatably mounted in the breechcase about the breechblock for longitudinal sliding movement, and means for locking the breechblock by transforming into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, which relative movement takes place after the breechblock has substantially reached its front closing position at which it closes off the rear end of the barrel, the improvement wherein: said breech mechanism includes a blocking means operable at the end of unlocking movement of the breechblock for positively holding the casing in a rearward position relative to the breechblock and for preventing relative movement between the breechblock and the casing upon further rearward movement of the breechblock and the casing; said blocking means including a longitudinal strip carried by the breechblock, the rearward end of said longitudinal strip being urged away from the breechblock into the path of the casing, a push-piece passing through the casing and engaging the rearward end of the strip, and a release means for causing the push-piece to move the strip towards breechblock, out of the path of the casing just before the locking movement of the breechblock, thereby permitting forward movement of the breechblock relative to the casing to lock the breechblock.

15. A breech mechanism as in claim 14 wherein said breechblock includes front and rear cylindrical portions separated by an enlarged cylindrical portion of greater diameter than the first two said cylindrical portions, and said casing includes an internal cylindrical recess, the front and rear ends of which are in fiuidtight contact with the front and rear cylindrical portions of the breechblock, respectively, said recess being large enough in the radial direction to accommodate the enlarged portion, and of sufiicient length between the ends to permit longitudinal movement of the casing relative to the breechblock, said leaf spring being movable into the path of the said rear end of the said recess, whereby when the rear end of the recess is rearward of the spring, and the spring is located outwardly away from the breechblock, the spring will prevent forward movement of the casing relative to the breechblock.

16. A breech mechanism as claimed in claim 15 wherein the casing comprises a pair of complementary, generally cylindrical shells adjoining each other in a diametral plane of the casing and rigidly connected together by studs extending radially through the casing, said studs being located in the part of the casing which constitutes the said rear end of the recess.

17. A breech mechanism as claimed in claim 16 wherein said release means comprises a cam member fixed to the breechcase for operating the said push-piece to determine the position of the leaf spring.

18. In a breech mechanism of the type for use with an automatic or semi-automatic gun comprising a breechblock mounted in a breechcase having a barrel cooperating therewith, said breechblock adapted to be locked by cooperation between the barrel and locking lugs formed on the breechblock, means at the forward end of the breechblock for receiving the rear end of cartridges to be fired, a casing non-rotatably mounted in the breechcase about the breechblock for longitudinal sliding movement, and means for locking the breechblock by transforming into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, which relative movement takes place after the breechblock has substantially reached its front closing position at which it closes off the rear end of the barrel, the improvement wherein: the said locking lugs are formed in and spaced about the periphery of the breechblock in at least two rows, the rearward face of the lugs of each row being located on a common helical skew path, the two skew paths being substantially identical to each other and separated axially by a distance greater than the common pitch distance of the skew helical paths.

19. A breech mechanism as claimed in claim 18 wherein an extractor means is carried by the breechblock, the said forward end of the breechblock comprises a cupshaped recess, and said locking lugs are formed on and spaced about the periphery of the exterior of the breechblock, and a longitudinal recess is formed in the exterior surface of the breechblock in a longitudinal space between the locking lugs for receiving a cartridge extractor means, and wherein the beginning and ending of each said row of lugs borders said longitudinal space.

20. A breech mechanism according to claim 18, wherein at least the rear faces of the lugs of the breechblock are located on skew helical surfaces whose inclinations are such that rearward movement of the breechblock is prevented;

21. A breech mechanism according to claim 18, wherein at least the rear faces of the breechblock lugs are located along skew helical surfaces whose inclinations are such that reversibility of the movement is permited.

22. In a breech mechanism of the type for use with an automatic or semi-automatic gun comprising a breechblock mounted in a breechcase having a barrel cooperating therewith, said breechblock adapted to be locked by cooperation between the barrel and the breechblock, a cup-shaped recess at the forward end of the breechblock for receiving the rear end of cartridges to be fired, a firing pin movable with respect to the breechblock and continuously urged towards the cup-shaped recess by a firing pin spring, a casing mounted in the breechcase about the breechblock for longitudinal movement in the breechcase, said casing being operatively connected to both the breechblock and the firing pin for performing, during its forward longitudinal movement, (a) a locking stroke wherein the breechblock is locked and then (b) a safety stroke, whereby the firing pin is moved forwardy reative to the breechblock, during said forward longitudinal movement of said casing, to enter the cup-shaped recess and fire the cartridge, said firing pin being connected to said casing through a lost motion connection such that the firing pin and said casing can perform relative longitudinal movement with respect to each other, said firing pin spring maintaining said firing pin in its forward position with respect to sad casing such that said firing pin enters the cup shaped recess to fire the cartridge after the casing has substantially completed its locking stroke but before the casing has completed its safety stroke, and said lost motion connection permitting said casing to move forward with respect to said frame pin to complete its safety stroke, after said cartridge has been fired. I

23. A breech mechanism according to claim 22, wherein the firing pin has a mass such that it opposes rebounding of the casing.

24. A breech mechanism as claimed in claim 22 wherein the breechblock includes external lugs positioned to rotate relative to internal lugs on a sleeve member rigid with the barrel to lock the breechblock relative to the barrel, and mechanical means between the casing and the breechblock for transforming longitudinal movement of the casing into rotating movement of the breechblock for locking the breechblock, when the breechblock has substantially reached its front closing position at which it closes off the front end of the barrel.

References Cited UNITED STATES PATENTS 853,715 5/1907 Mondragon 89-l85 X 1,603,684 10/1926 Garand 89-185 X 1,743,472 1/1930 Meyer 89185 X 2,035,539 3/1936 Dicke 89-185 2,388,291 11/1945 Ruger 89185 X 2,685,754 8/1954 Crittendon et al. 89185 X 3,057,100 10/1962 Dixon 89-185 X SAMUEL FEINBERG, Primary Examiner S. C. BENTLEY, Assistant Examiner 

